UVA - 12542 - Prime Substring

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.LinkedList;

public class Main {
  
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringBuffer sb = new StringBuffer("");
        int[]arr=sievePrime(1000*100);
        while(true){
            String str=br.readLine();
            if(str.equals("0")){
                break;
            }
            for(int i=arr.length-1;i>-1;i--){
                if((arr[i]+"").length()<str.length()){
                if(findPattern (arr[i]+"",str)){
                    sb.append(arr[i]).append("\n");
                    break;
                }
                }
            }
        }
        System.out.print(sb);
    }
  
     static boolean findPattern(String Pattern,String str){
        int count=0;
        for(int i=0,j=0;i<str.length();i++){
            if(Pattern.charAt(j)==str.charAt(i)){
                count++;
                j++;
            }else{
                j=0;
                count=0;
            }
            if(count==Pattern.length()){
                return true;
            }
        }
        return false;
    }
     static int[] sievePrime(int x) {
        boolean[] notPrime = new boolean[x + 1];
        notPrime[0] = true;
        notPrime[1] = true;
        for (int i = 2; i * i < x + 1; i++) {
            if (!notPrime[i]) {
                for (int j = i; i * j < x + 1; j++) {
                    notPrime[i * j] = true;
                }
            }
        }
        LinkedList<Integer> list=new LinkedList<Integer>();
        for (int i = 2;i < x; i++){
            if(!notPrime[i])
                list.add(i);
        }
        int arr[]=new int[list.size()];
        for (int i = 0;i < arr.length; i++){
            arr[i]=list.get(i);
        }
        return arr;
    }
}